The present invention pertains generally to pulse circuit devices and more particularly to inductive storage pulse circuit devices.
With the advent of pulse lasers and other such devices which require electrical pulse energy for operation, the requirements for a device capable of producing repetitive high power pulses of electrical energy have increased greatly. In applications where pulse power is needed for a limited period, energy storage systems have many practical advantages over continuous duty power sources. The high energy storage density of inductors (2-20 MJ/m.sup.3) versus the energy storage of capacitors (0.2 MJ/m.sup.3) is the controlling factor favoring inductive storage systems over capacitive storage systems, particularly for large scale applications where size, weight, and cost are overriding considerations.
Utilization of inductively stored energy normally requires the interruption of a charging current with an opening switch, as illustrated in FIG. 1. FIG. 1 schematically illustrates a simplified inductive energy storage and transfer system. The power supply 10 which is usually a relatively low voltage power supply, charges the energy storage coil 12 through switch 14 to a peak current level I.sub.0. Switch 14 must be capable of carrying the coil current during the charge and hold times with low dissipation. To cause the current to transfer to the load 16, switch 14 must be rapidly opened to rapidly increase its impedance to a value much greater than the impedance of load 16. After transfer of energy from the switch 14 to the load 16, the opening switch must withstand the recovery voltage generated by the load. For repetitive operation, the switch must close again to terminate each output pulse and then repeat the opening/closing cycle. The obtainable pulse rise time, pulse width, and pulse repetition rate are all dependent upon the operational characteristics of switch 14. Since requirements for pulse circuit devices have increased dramatically, it is desirable to control these parameters separately to provide desired pulse wave characteristics at high power levels.
To achieve the desired parameters regarding pulse repetition frequency, pulse rise time, etc., prior art devices have attempted to improve the characteristics of opening switch 14 illustrated in FIG. 1. A number of these prior art methods are disclosed in the Proceedings of the Workshop on Repetitive Opening Switches (Jan. 28-30, 1981, Durango, Colo.) published Apr. 20, 1981. Some of the methods disclosed of achieving repetitive energy transfers include the use of a dense plasma focus switch, an electron beam controlled switch, a magnetically controlled vacuum arc switch, and multiple fused or explosively actuated switches. The dense plasma focus switch suffers from loss of control once operation is initiated, erratic self-triggering, a high conduction drop, and a minimum current level required for operation. The electron beam controlled switch suffers from a high conduction drop and the requirement of an external electron beam source. The vacuum arc switch suffers from high switch dissipation during interruption, the requirement of an external magnetic field source, and apparent difficulty in scaling to much higher power levels. Fuses and explosively actuated switches suffer from the obvious requirement of the necessity for an additional element for each output pulse desired.